[binutils-gdb] gdb/riscv: Remove partial target description support

[sergiodj+buildbot at sergiodj dot net]

*** TEST RESULTS FOR COMMIT 9add17f218409f357d5ed8b831c777ac93f41ec4 ***

Author: Andrew Burgess <andrew.burgess@embecosm.com>
Branch: master
Commit: 9add17f218409f357d5ed8b831c777ac93f41ec4

gdb/riscv: Remove partial target description support

Some parts of the target description support were committed with the
initial riscv patch.  As target descriptions are not currently supported
on riscv this commit removes the two pieces for code that relate to
target description support.

It is expected that target description support will be added in the
future, at which point this, or similar code will be added back.

gdb/ChangeLog:

	* riscv-tdep.c (riscv_register_name): Remove target description
	support.
	(riscv_gdbarch_init): Remove target description check.